Merge pull request hacktoberfest17#474 from sconetto/prime-number

Fix hacktoberfest17#473

Author: t2013anurag

prime_number/prime_number.c

@@ -0,0 +1,26 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <math.h>
+
+bool prime(long long n) {
+	if (n < 2) return false;
+	if (n == 2) return true;
+	if (n % 2 == 0) return false;
+	for (int i = 3; i <= sqrt(n); ++i)	{
+		if (n % i == 0) return false;
+	}
+	return true;
+}
+
+int main(int argc, char const *argv[]) {
+	long long n;
+	bool aux;
+	scanf("%lld", &n);
+	aux = prime(n);
+	if (aux == true) {
+		printf("it's prime!\n");
+	}
+	else
+		printf("it's not prime!\n");
+	return 0;
+}